Image Credit: All photos: Roger Normand
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[Editor’s note: Roger and Lynn Normand are building a [no-glossary]Passivhaus[/no-glossary] in Maine. This is the 24th article in a series that will follow their project from planning through construction.]
The foundation for the main house is complete. It’s time to start framing and sheathing the main floor deck while we wait for Shawn Woods to excavate the footings for the attached slab-grade garage and three season room.
There’s not a whole lot of “greenness” or “Passivhausness” to talk about in floor framing. But it’s all part of the construction process and hey, we need a main floor to walk on.
The framers — Jason, Travis, Jimmy, and John — began building the main floor deck by applying a capillary break on the top of the concrete in the Logix ICF foundation to stop any moisture from wicking up into the floor framing.
They then compared the “as is” foundation to the architectural plans. It’s best to start framing the deck on a level and square foundation. That’s especially true for EdgewaterHaus, as the main floor walls and roof trusses are already built in a factory to the specifications of the architectural plans; it’s too late to make any dimensional accommodations to the walls or trusses.
A small 1/8-inch gap at the bottom of the wall on a problematic foundation can become a gaping 1/2-inch opening 10 feet higher at the top of the wall, complicating the placement of adjacent wall panels and the trusses. If this were a typical home, such gaps would be shimmed and covered by exterior and interior finishes; no one would know the difference. Not us. Gaps complicate air sealing the building envelope. The blower door and thermal imagery will reveal these “thermal holes.” We need an exceptionally tight, well-assembled building envelope to meet the Passivhaus standard.
So if there’s any shimming, it’s best to do it at one place — the bottom plate of the wall. Jason used a laser to methodically check the elevation of the foundation at each point near the wall anchors and measured wall dimensions against the specifications of the plan.
Uh-oh.
Elevation problems
Using the highest point on the foundation as a reference, Jason found two areas with notable variation: the west side of the Bedroom 3 foundation was 1/2 inch low, and the south side of the three-season room foundation was 3/4 inch low.
The foundation was also out of square. Using the south facade as a reference line, the north wing of the building foundation strays from the 60 degree design by up to five degrees. That’s not much, except when the wall extends 50 feet!
The east and west foundation walls of the north wing are not parallel to each other; the foundation is 1 3/4 inch too wide where the garage wall meets the house, expanding to 2 1/2 inch too wide at the far, north side of the garage.
Uh-oh.
I expected tolerances to be closer
Now some may say that’s just another day in the life of a framer to resolve real-world variation in the foundation.
Perhaps. But I expected better results with the Logix foundation. We had surveyors precisely mark the outside corners of the Logix blocks on the footers. And the snug fit of the many male/female vertical connections points in the Logix block adds confidence. I’m not sure if the vertical and horizontal variance lies in how the blocks were stacked and braced, or the shifting of some block while the concrete was poured into the Logix cavity, or both.
Several areas of Logix did noticeably lift during the pour, then seemed to settle back into place as more concrete was poured. Yet in looking at the completed foundation, there are clearly vertical and horizontal gaps ranging from 1/8 inch to 3/8 inch in many of the Logix blocks.
The worst areas are the top two courses of block, and the very worst is the east section of the wall with the 60 degree angle in the foundation. The vertical supports did not extend to the top two courses of the Logix, and not every course of block was screwed into the vertical supports to prevent uplift.
Concrete exerts enormous pressure when it is being poured. Could better bracing and checking for plumb to the bottom course have improved the results?
Squaring and leveling the foundation
The framers spent several man days adjusting the horizontal and vertical position of the base plates on the foundation to bring the floor framing back to the plan specifications. That meant moving the mudsill inward or outward on the foundation, and shimming it upwards by as much as 3/4 inch. Jason aimed to have dimensions and elevations to a +/- 1/8 inch tolerance across the entire foundation.
The framers next cut, placed, and braced the seven concrete-filled lally columns in the basement, secured two LVL beams atop several of the lallys, and a delivery truck boomed two beefy steel I-beams into place atop the remaining lally columns.
Uh-oh.
It looks like we need another lally column
One of the steel I-beams had insufficient bearing on the foundation. That was quickly solved by placing another lally column on the footer where that steel beam meets the foundation.
Our floor was engineered by Coastal Forest Products. The framers started to install the I-beams and floor deck along the main axis of the house.
Uh-oh.
Another trip to the lumber yard
Coastal delivered the wrong mix of hangers: there were too many 3 1/2-inch-wide hangers and not enough 2 1/2-inch-wide hangers, and there were not enough top-mount hangers for use on the steel beams. We were also short on a section of rim board and some sheathing.
That was solved the next day. Floor framing proceeded along the main axis of the house.
The crew then started the layout for the hangers on the north wing, the one with the 60 degree angle.
Uh-oh.
Where can I get some 60-degree hangers — fast?
We had received 45 degree hangers instead of the 60 degree hangers called out in the design.
The Coastal rep came on site, confirming the shortage. Sixty degree hangers are a special order item. He promised quick delivery, especially if they had some in stock.
And so we await delivery of the 60 degree hangers to complete the main floor deck.
Meanwhile, the installed deck is rock solid. There’s absolutely no bounce on the floor, even before we pour the 1 1/2-inch concrete. The meticulous care to square and level the foundation bodes well for installing the factory-built panels.
The first article in this series was Kicking the Tires on a Passivhaus Project. Roger Normand’s construction blog is called EdgewaterHaus.
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14 Comments
Misery loves company
I think everybody likes to read about the everyday little snags that must be overcome in order to take a house from designed to built. It makes me feel better about the snags I hit in my projects, anyway!Interesting read, thanks for sharing.
Roger,
What is the advantage
Roger,
What is the advantage of the Logix foam block forms, as opposed to using steel or wood forms?
Ron Keagle: you should read
Ron Keagle: you should read about ICF in general and not only the LOGIX brand.
Advantages are various depending on the project.
Some say it is somewhat faster setup when accounted for the auto. installed insulation.
I'd say if you have a very good steel/wood forming team, there is not much advantages with ICF VS
regular formed concrete ( and u can choose where the insulation is located and which insulation you are using when using forms .. )
Roger : the block height gaps is very unfortunate ... maybe it is a Logix design defficiency ?
Have you got the walls measured for plumb finally ?
3/4" height difference on a single story foundation is not something to be proud of ...
Have you calculated the additional costs incurred by the ICF basement walls problems ??
So...
Roger,
What's the plan for airsealing those big gaps between the shims under your mudsill?
I'm guessing sprayfoam?
Regarding those gaps,
Regarding those gaps, wouldn't they need to be entirely filled with some type of grout in order to transfer the compression loading through the sill and into the concrete wall?
Roger responds
The Logix web site touts many advantages. What sold me on the system was the expectation of saving time and money for the foundation + required insulation to achieve the Passive House standard. I had a demo of the product. They stack like Lego blocks. How hard can that be? In hindsight, there is far more skill and knowledge to success than Logix suggests. I have not calculated the additional costs. It took our lead framer some 40 hours to get to level and square. Don't know how much faster it would have been with a more traditional foundation. I have used spray foam from the outside and the inside of the foundation to fill the gaps. The cedar shims should transfer the weight to the foundation.
Gaps under mudsill
When I've had to confront that, I've used mason's mix to build up a level pad from bolt to bolt. Otherwise your sill seal does nothing.
slc
I saw once on a Japanese house blog that they leveled up the foundation with self-leveling compound, due to pre-cut framing with tight tolerances.
I don't see how you can prop
I don't see how you can prop up the sill on shims every few feet or few yards, and then place a coninuous compression load on that sill. Won't the stud loading sag the sill back down to the concrete in the spans between the shims?
Furthermore, that 3/4" sag will gradually develop as the walls and roof loading are added during construction, and thus throw everything out of whack.
That worked for shimming my
That worked for shimming my 1940s cape, but it has 6x6 sills. So I'd be putting a lot more shims in to spread the load.
Continuous sill support
Well, a 6 X 6 would be able to structurally span the shims like a bridge. But with a 1-1/2" sill plate, you would need a shim directly under each stud. If I were leveling the foundation wall, I would set and level small micro forms, pour in grout, and strike it off level for a continuous, level cement bed atop the unlevel foundation wall. The sill needs continuous support.
Holy Cow! Little problems?!
Wow. Doesn't this seem a *bit* excessive on the problem side? Is there anything that went right? LOL. When will it stop?
Based more on common sense than engineering background, I second the questionable method of shimming each anchor bolt. It sounds like you're taking the most important load carrying point and weakening it. There may not be a detrimental affect, but why risk it? Not that a more appropriate, continuous fix is all that easy to achieve...Having not designed around or seen ICF being installed, I can imagine the challenge of getting lightweight forms to behave during the pour, but there must be a method to successfully brace these forms to avoid lift and movement...is that worth of a post in and of itself? Maybe on another blog?
Good luck on tightening things up as you move along!
Don't blame the ICFs...
Sounds like the ICF blocks were not properly anchored to the footer or to each other. I don't know that brand, but we used Arxx which recommends (requires?) their "hooks" and "claws" (metal clips), or even just large zip ties, to tie the blocks to each other. You only have to do this at the bottom and at the corners, however. We only had one separation larger than 1/16" in 430 feet of wall (26' to the gables!) and that was due to an installation error (we cut a block and didn't adequately strengthen the connection to the adjacent block when the standard hook didn't fit). And we're amateurs.
As for the positioning problems, again, this is a result of bad technique: If you use bracing, which should be screwed to the footing (e.g., with Tapcons), there's no chance of the blocks moving or leaning. We bought our bracing set on Craiglist, then sold it for more than we paid for it (we cleaned them up a little, and took better pictures ;-)
We're very happy with our ICF walls: They're weatherproof (even hurricane and tornado proof!), soundproof, and provide excellent insulation and thermal mass benefits. But windows and other openings are a *lot* of work and so it's really a technology better suited to high-end homes or industrial buildings with relatively few openings than to smaller homes where there are more smaller openings and where the budget is likely to be bigger concern. They're still a no-brainer for foundation and basement walls, though.
Oh, and as for that "capillary break", a better solution to that problem is Fastfoot. We didn't even anchor it with spikes like the manufacturer recommends (don't really need this as long as the wind isn't blowing on your pour day) and so our footing stays bone dry even though it's actually sitting in water several months of the year (drain tile is at the bottom of the footing).
Better way than shims? Maybe.
It's very common practice in these parts to use cedar shims to shim a wall level in this manner. Does that mean it's the best way? Perhaps not. I'll certainly think about this for my next project, but for this project I'm really not concerned. The walls will act as a system as they are tenaciously fastened and the studs and plates are sealed to the sheathing with continuous construction adhesive. I expect typical wood shrinkage to be more of a problem than any sagging in the wall between shims.
Chris
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